On Jan. 4, 1996, a joint Army, Navy and Air Force team began the 22-day Army Mountain Top Experiment, or AMTE, at the Pacific Missile Range Facility, Barking Sands, Kauai, Hawaii.

Forgotten by many, AMTE, also called Mountain Top, was a significant step in the development of cruise missile defense. Since Operation Desert Storm five years early, the number of cruise missiles had increased dramatically. Their unpredictable flight patterns combined with the Earth's curvature created a challenge for cruise missile defense programs. The Mountain Top Experiment, Phase I of a Navy Cruise Missile Defense Advanced Concept Technology Demonstration, or ACTD, however validated the "potential to engage a cruise missile beyond the line-of-sight of current ground-based radars using existing air defense doctrine."

Approved by the deputy under secretary of Defense (Advanced Technology) in May 1994, the chief of Naval Research administered the ACTD. Navy activities were coordinated through the Program Executive Office for Theater Missile Defense and the Cooperative Engagement Capability program manager. Army activities meanwhile were coordinated by Brig. Gen. Richard Black, PEO for Missile Defense, and Dale More, the AMTE program manager with the assistance of personnel from the U.S. Army Space and Strategic Defense Command, the U.S. Army Missile Command, the Air Defense Artillery School, White Sands Missile Range and the 11th Air Defense Artillery Brigade.

The ground- or surface-based systems used in these tests included a Patriot battery located at the Kauai test facility and an Aegis cruiser, the USS Lake Erie. Meanwhile atop the Kokee Mountain at an elevation of 3,800 feet, additional test equipment included a Radar Surveillance Technology Experimental Radar, or RSTER, which provided surveillance and tracking, an MK 74 Fire Control System for tracking and target illumination, and the CEC system, which relayed data to the ground-based elements.

The Air Force's Airborne Early Warning and Control or AWACs also supported this initiative. In the captive carry tests, a sensor under development for the Patriot Advanced Capability-3 was suspended beneath an Air Force C-130.

The issues for this test were twofold. Could an airborne (or mountain-top) radar detect and track the targets and relay the necessary information to the ground-stations? Second, could the data be properly analyzed to address issues caused by, for example, the curvature of the Earth and the location or elevation of the radar vice the location or elevation of the interceptor?

In the Army experiments tracking data was collected by the MK-74 situated atop the mountain. The CEC processor transmitted the information via the Joint Tactical Information Distribution System, or JTIDS, to a Patriot battery located at the PMRF. The battery developed fire control and acquisition solutions for the PAC-3 seeker. As this seeker was still in a developmental stage, a prototype seeker was suspended beneath the C-130 with a Virtual Engagement Simulation Tool or VEST. The VEST provides "a real-time, high fidelity virtual engagement interceptor simulation," which negated the requirement for live fire tests. With the data provided by the CEC, the seeker would move the turret in the appropriate direction to track the target.

In the subsequent Navy Mountain Top Experiment conducted Jan. 20-21, BQM-74 E target drones were flown inbound at low altitudes and at distances beyond the ranges of the Aegis and Patriot weapon systems. The target drones were launched from the PMRF and at a distance beyond the range of the radar turned to head back toward shore or the ship. In these tests the target was then detected by the RSTER and tracked by the MK 74 radar. The CEC created a composite track which was provided to the two weapons systems. The USS Lake Erie launched four standard missiles and achieved four target kills. These intercepts were achieved at ranges greater than three times that of the typical system.

During the AMTE and the follow-on Joint Data Collection, a total of 112 captive carry tests and virtual engagements were conducted. Of these, 101 were deemed successful. There were nine no-tests (issues/anomalies not attributable to the Mountain Top system) and only two failures. Thus they effectively created a networked architecture that allowed surface-based systems to engage targets beyond the capabilities of their associated radars. Thereby demonstrating a capability to extend the horizon of the protected area further than the line of sight enabling them to engage low-flying cruise missiles.